Note Stock-based compensation - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized	$ 7,900,000		$ 7,900,000
Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition			2 years 5 months
Restricted Stock Units (RSUs)
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Windfall Net Of Shortfall	$ 800,000
Restricted Stock Units (RSUs) | TARP Interim Final Rule
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights			Under the Incentive Plan, the Corporation has issued restricted shares, which become vested based on the employees’ continued service with Popular. Unless otherwise stated in an agreement, the compensation cost associated with the shares of restricted stock is determined based on a two-prong vesting schedule. The first part is vested ratably over five years commencing at the date of grant (the “graduated vesting portion”) and the second part is vested at termination of employment after attainment of 55 years of age and 10 years of service (the “retirement vesting portion”). The graduated vesting portion is accelerated at termination of employment after attaining 55 years of age and 10 years of service. The vesting schedule for restricted shares granted on or after 2014 was modified as follows, the first part is vested ratably over four years commencing at the date of the grant (the “graduated vesting portion”) and the second part is vested at termination of employment after attainment of the earlier of 55 years of age and 10 years of service or 60 years of age and 5 years of service (the “retirement vesting portion”). The graduated vesting portion is accelerated at termination of employment after attaining the earlier of 55 years of age and 10 years of service or 60 years of age and 5 years of service.
Restricted Stock Units (RSUs) | Executive Officers
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period	0	0	138,516	279,890
Restricted Stock Expense	$ 1,000,000	$ 1,000,000	$ 4,800,000	$ 6,600,000
Employee Service Share Based Compensation Tax Benefit From Compensation Expense	$ 200,000	$ 200,000	900,000	$ 1,200,000
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Total Fair Value			6,400,000
Restricted Stock Units (RSUs) | Executive Officers | Share Vesting On Grant Date
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Total Fair Value			$ 4,400,000
Restricted Stock Units (RSUs) | Directors
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period	0	0	25,771	40,517	40,517
Restricted Stock Expense	$ 300,000	$ 300,000	$ 1,000,000	$ 800,000
Employee Service Share Based Compensation Tax Benefit From Compensation Expense	$ 39,000	$ 31,000	100,000	$ 84,000
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Total Fair Value			$ 1,000,000
Performance Based Shares | Executive Officers
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period	0	0	73,684	64,598
Restricted Stock Expense	$ 300,000	$ 100,000	$ 2,400,000	$ 1,300,000
Employee Service Share Based Compensation Tax Benefit From Compensation Expense	$ 42,000	$ 11,000	$ 200,000	$ 100,000
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights			The number of shares that will ultimately vest ranges from 50% to a 150% of target based on both market (TSR) and performance (EPS) conditions. The performance shares vest at the end of the three-year performance cycle. The vesting is accelerated at termination of employment after attaining the earlier of 55 years of age and 10 years of service or 60 years of age and 5 years of service.